Method for manufacturing touch screen linearization pattern

ABSTRACT

A novel method for manufacturing touch screen linearization pattern which is necessary for five wire resistive type or current sensing type touch screen, and directly affects the accuracy, producing price and border area size of the touch screen, includes to print a linearization pattern on the border area of a conductive glass surface with a selected ink. The ink is made by blending high conductive silver powder between about 59% to 62% in weight and carbon powder between about 14% to 16% in a contact agent solvent between about 24% to 25% in weight. The touch screen thus formed has resistance value ratio of about ten between the square surface of the glass layer and the two ends of the linearization pattern.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a novel method for manufacturing touch screen linearization pattern and particularly a method of producing a linearization pattern that is capable of increasing resistance ratio of glass surface unit square against two ends of the linearization pattern.

[0002] Presently, voltage sensing type touch screen and current sensing type touch screen have been widely used in desk top computers, handheld computers or notebook computers. Users may write, draw pictures or select various function or press command keys on the screen to generate electric signals and input into the computer to perform processes desired. When in use, the computer makes switching of functional windows on the screen, and users do not have to operate the computer through the keyboard.

[0003] The touch screen set forth above (as shown in FIG. 1 for a traditional current sensing type touch screen) usually includes a glass layer 1, a conductive membrane layer 2, a linearization pattern 3, an isolation layer 4, a four wire silver printing layer 5 and a tail cable 6 connecting to a controller. The controller outputs four equal voltages to four linearization ends of the touch screen to measure current variation.

[0004] When different point of the touch screen is touched, the current at the four ends will have different changes. Through measuring the current variation, the controller can determine the touched position. Detailed operation principle may be found in U.S. Pat. No. 4,293,734. In practice, the design of linearization pattern directly affects the accuracy, price and occupied space of the touch screen. Earlier linearization pattern consists of discrete resistor elements linking to the border area of the touch screen to form a resistor network. This type of resistor network is not desirable either in manufacturing or final accuracy of the touch screen. Later, a technique of forming linearization pattern by printing was developed. Reference can be found in U.S. Pat. No. 3,798,370. However, same as before, its linearization pattern occupies a relatively large border area of the touch screen and results in less useful area for the touch screen. In the present LCD development, border area becomes smaller constantly, large size linearization pattern will have little or no market acceptance. In the past, there was a concept for making the touch screen linearization pattern disclosed in U.S. Pat. No. 3,591,718. However it does not provide a practical method for manufacturing, and the concept never materializes commercially.

[0005] There is another type of touch screen (as shown in FIG. 2, a traditional voltage sensing type five wire touch screen) which includes a glass layer 7, an Indium Tin Oxide (ITO) conductive layer 8, a linearization pattern 9, a set of insulation points 10, an isolation layer 11, a four wire silver printing layer 12, another isolation layer 13, another ITO conductive layer 14, a plastic membrane layer 15 and a tail cable 16 linking to a controller. In operating principle, the lower ITO links to an even electric field of 0-5V in X-axis direction. When the touch screen is touched, the upper ITO layer contacts the lower ITO layer and measures the voltage value. The voltage ratio represents the positional ratio on the touch screen in that direction (X-axis). For instance, 3V represents the touch point is located at 60% of the total length in the X-direction. When measuring of one direction (i.e. X-axis) is finished, the controller panel converts the lower ITO to an even electric field of 0-5V in Y-axis direction, then uses the lower ITO layer to measure the voltage value of touch point at the upper layer and measure the position in another direction (Y-axis). Reference details can be found in U.S. Pat. No. 3,798,370. This type of touch screen also needs linearization pattern to increase accuracy. In this type of touch screen, ELO's five wire resistive touch screen is the most popular on the market. ELO's linearization pattern is made by forming resistor network from separated silver paste, and adding and removing some of the conductive sputtering layer to increase the accuracy of the linearization pattern used on the touch screen. However, ELO's touch screen still has a lot of linearization deficiency at the border corners. The process of removing the conductive layer also increases the production cost of the touch screen.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of this invention to overcome the foregoing disadvantages by blending high conductive material such as silver powder and carbon powder and contact agent solvent to form a printing ink, then using the ink to print an even resistor line at the border area of the touch screen to form a connected resistor network to serve as linearization pattern thereby to increase accuracy of the touch screen and reduce production cost and reduce the border area being used.

[0007] Another object of this invention is to use other high conductive metallic material such as copper powder. By changing relative material contents, a desirable resistance coefficient may be obtained thereby to produce a linearization pattern desired. During making material composition arrangement, the size and thickness of the pattern may be used to compensate the conductivity overshoot or deficient of the material to ensure that the final resistance ratio of each square of glass surface against two ends of the linearization pattern reaches about ten. In one aspect, this invention provides a blended material for printing the required resistance value to couple with existing ITO conductive glass now available on the market to produce a low cost touch screen that has high accuracy and more useable area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention, as well as its many advantages, may be further understood by the following detailed description and drawings.

[0009]FIG. 1 is a schematic exploded view of a conventional current sensing type touch screen.

[0010]FIG. 2 is a schematic exploded view of a conventional five wire voltage sensing type touch screen.

[0011]FIG. 3 is a schematic view of a first improved linearization pattern based on the linearization pattern layer shown in FIGS. 1 or 2.

[0012]FIG. 4 is a schematic view of a second improved linearization pattern based on the linearization pattern layer shown in FIGS. 1 or 2.

[0013]FIG. 5 is a schematic view of a third linearization pattern according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Referring to FIG. 3 for a first linearization pattern structure made by the method of this invention based on the linearization pattern layer shown in FIGS. 1 and 2, it is aiming to improve the linearization patterns at the linearization layer 3 and 9 for increasing the accuracy of the linearization of the touch screen.

[0015] As the resistance ratio of per square surface of the glass layer 1 or 7 (shown in FIGS. 1 and 2) against that of the two ends of the linearization pattern 3A, and the evenness of the linearization pattern 3A determine the accuracy of the touch screen, the linearization pattern 3A used in this invention is formed by printing method which prints high conductive material on glass layer 1 or 7 sputtered with low conductive material or other material. Hence the linearization pattern 3A is very even. The only factor which determines the linearization accuracy of the touch screen is the ratio of resistance of per square surface of the glass layer 1 and 7 (shown in FIGS. 1 and 2) against that of the two ends of the linearization pattern 3A. Higher ratio value means higher accuracy. However when the value is too high, it becomes difficult for the controller to measure. Hence in practice the value is controlled at about ten. The resistance value of per square surface of the glass layer 1 or 7 may be selected form the what have been available on the market, for instance, but not limited to, ITO glass from MERCK with 500 Ω per square or ITO glass from AVCT with 1500 Ω per square. The resistance value at the two ends of the linearization pattern may be calculated by the following equation:

R=(ρL)/(WH)

[0016] Where ρ is resistance coefficient determined by material, and may be changed by the ratio of acceptable silver and carbon powder. L is length, W is width, and H is height. Hence the resistance value of the two ends of the linearization pattern 3A may be changed through controlling of printing. (Once using aforesaid equation to derive the resistance value and compare with the ITO resistance value being used, the resistance ratio between the glass 1 or 7 and linearization pattern 3A may be obtained.)

[0017] The first linearization pattern structure set forth is formed by printing of a selected ink on the surface of the conductive glass ITO (the glass layer 1 and 7 shown in FIGS. 1 and 2). The ink is made by blending high conductive silver powder 62% and carbon powder 14% in a contact agent solvent (or adhesive) 24% in weight. When the linearization pattern 3A is being printed, it has a thickness of 10 micro meter which has resistance of 0.5 ohm per square. The linearization pattern 3A has a width of 3 mm and a length of 300 mm at each side to form a 100 square. The two ends have resistance of 100 ohm, and the ITO glass has 500 ohm per square. The linearization accuracy of the touch screen is higher than 99% when formed by resistance ratio of 10 to 1 between the ITO resistance and linearization patterns at two sides.

[0018]FIG. 4 illustrates a second linearization pattern structure made by the method of this invention based on the linear pattern layer shown in FIGS. 1 and 2. The linearization pattern 3B is printed by an ink made by blending high conductive material of silver powder 59% and carbon powder 16% in a contact agent (or adhesive) solvent 25% in weight. When the linearization pattern 3B is being printed on the surface of the conductive glass ITO (as the glass layer 1 and 7 shown in FIGS. 1 and 2), it has a thickness of 10 micro meter which has resistance of 1 ohm per square. The linearization pattern 3B has a width of 3 mm and a length of 300 mm at each side to form a 100 square. The two ends have resistance of 100 ohm, and the ITO glass has 1000 ohm per square. The linearization accuracy of the touch screen is higher than 99% when formed by resistance ratio of 10 to 1 between the ITO resistance and linearization patterns at two sides.

[0019] It is to be noted that the embodiment examples set forth above are not contemplated to limit silver and carbon powder as the only choice of high conductive material. Other metallic material may be used as substitute, such as copper powder. A desire resistance coefficient may be obtained by changing the relative contents and to form desirable liner patterns. In the process of blending the material, it is also possible to change pattern size and height to compensate the conductivity overshoot or deficient of the material to ensure that the final resistance value ratio between the square surface of the glass and the linearization pattern reaches about ten.

[0020] Furthermore, besides forming the linearization pattern 3A and 3B at the border area set forth above, the linearization pattern may also be printed in lines form 3C (as shown in FIG. 5). 

What is claimed is:
 1. A method for manufacturing touch screen linearization pattern using a blended material for making the linearization pattern, wherein the blended material comprises high conductive material which includes silver powder, carbon powder and contact agent solvent.
 2. The method of claim 1, wherein the silver powder is between about 59% to 62% by weight.
 3. The method of claim 1, wherein the carbon powder is between about 14% to 16% by weight.
 4. The method of claim 1, wherein the contact agent is adhesive and is between about 24% to 25% by weight.
 5. The method of claim 1, wherein the high conductive material is other metallic material including copper powder and has changeable relative composition to attain resistance coefficient desired whereby to form desired linearization patterns, the size of the patterns being changeable to compensate conductivity overshoot or deficient of the material to maintain final resistance value ratio between the square surface of the glass and two ends of the linerization pattern about ten.
 6. A method for manufacturing touch screen linearization pattern with a touch screen including a glass layer, a conductive membrane layer, a linearization pattern, an isolation layer, a four wire silver printing layer and a tail cable linking to a controller, the controller output four equal voltage to four ends of the touch screen and measuring current variation, comprising the steps: making an ink by blending high conductive material of silver powder in a percentage weight range between about 59% to 62% and carbon powder between about 14% to 16% in a contact agent solvent between about 24% to 25%; and using the ink to print a linearization pattern on the border area of the conductive glass layer surface to form a linearization pattern such that resistance value ratio between the square surface of the glass layer and two ends of the linearization pattern being controlled at about ten.
 7. The method of claim 6, wherein the glass layer is made of Indium Tin Oxide glass which has resistance value of 500 Ω per square or 1500 Ω per square.
 8. The method of claim 6, wherein the resistance coefficient of the linearization pattern is determined by the material and is changeable through variation of the contained acceptable silver powder and carbon powder, and is changeable by the size and shape of the linearization pattern.
 9. The method of claim 6, wherein the linearization pattern has a height of 10 micro meter which has resistance of 0.5 ohm per square, and has a width of 3 mm and a length of 300 mm to form 100 square and having resistance value of 100 ohm at two ends thereof, and using an Indium Tin Oxide glass which has 500 ohm per square thereby having a resistance ratio of ten between the Indium Tin Oxide resistance value and resistance value of the linearization patterns at two sides thereof.
 10. The method of claim 6, wherein the linearization pattern has a height of 10 micro meter which has resistance value of 1 ohm per square, and has a width of 3 mm and a length of 300 mm to form 100 square and having 100 ohm at two ends thereof, and using an ITO glass which has 1000 ohm per square thereby having a resistance ratio of ten between the ITO resistance value and resistance value of the linearization patterns at two sides thereof.
 11. A method of manufacturing touch screen linearization pattern with a touch screen including a glass layer, an ITO conductive membrane layer, a linearization pattern, a set of insulation points, an isolation layer, a four wire silver printing layer, another isolation layer, another ITO conductive layer, a plastic layer and a tail cable linking to a controller, the upper ITO being contactable to the lower ITO for measuring the voltage of the contact point, comprising the steps: making an ink by blending a high conductive material of silver powder in a percentage weight range between about 59% to 62% and carbon powder between about 14% to 16% in a contact agent solvent between about 24% to 25%; and using the ink to print a linearization pattern on the border area of the conductive glass layer surface to form a linearization pattern such that resistance value ratio between the square surface of the glass layer and two ends of the linearization pattern being controlled at about ten.
 12. The method of claim 11, wherein the glass layer is made of Indium Tin Oxide glass which has resistance value of 500 Ω per square or 1500 Ω per square.
 13. The method of claim 11, wherein the resistance coefficient of the linearization pattern is determined by the material and is changeable through variation of the contained acceptable silver powder and carbon powder, and is changeable by the size and shape of the linearization pattern.
 14. The method of claim 11, wherein the linearization pattern has a height of 10 micro meter which has resistance value of 0.5 ohm per square, and has a width of 3 mm and a length of 300 mm to form 100 square and having resistance value of 100 ohm at two ends thereof, and using an Indium Tin Oxide glass which has 500 ohm per square thereby having a resistance ratio of ten between the Indium Tin Oxide resistance value and resistance value of the linearization patterns at two sides thereof.
 15. The method of claim 11, wherein the linearization pattern has a height of 10 micro meter which has resistance value of 1 ohm per square, and has a width of 3 mm and a length of 300 mm to form 100 square and having resistance value of 100 ohm at two ends thereof, and using an Indium Tin Oxide glass which has 1000 ohm per square thereby having a resistance ratio of ten between the Indium Tin Oxide resistance value and resistance value of the linearization patterns at two sides thereof. 